Expansible rotary bit



ALusoN Filed Feb. 2, 1926 2 Sheets-Sheet 2 Sheets-Sheet 2 March 12, 1929. A. ALLISON EXPANSIBLE ROTARY BIT Filed Feb. 2, 1926 Patented Mar. 12, 1929.

UNITED STATES PATENT OFFICE.

ARTHUR ALLISON, OF LONG BEACH, CALIFORNIA.

EXPANSIBLE Application filed February This invention has to do with rotary drilling bits of the disk and other types, as used for drilling wells: and it may be stated as a general object of the invention to provide a. disk bit with a mechanism that makes it expansible for drilling a relatively enlarged hole below a smaller hole or below a. well pipe or for drilling a hole of more uniform diameter than usual through alternating hard and soft formations. In drilling a hole below a well pipe, it is sometimes desirable to bore a hole large enough that the well pipe through which the ,bit is passed down can be lowered into the drilled hole. In drilling a hole through alternating soft and hard formations an ordinary nonexpansiblc rotary bit will cause the hole to he made somewhat larger in soft formations than in hard formations. This variation in diameter of the hole is due first to the fact that a rotary bit will actually drill a somewhat larger hole in a soft formation and will drill in a hard formation a hole only substantially its own diameter. And also thewater circulation in the hole has a tendcncy to enlarge the diameter in soft formations. Consequently a. hole drilled with an ordinary non-expansible rotary bit is of substantially less diameter through hard formations than through soft formations; and in the hard formations is not large enough to pass the well pipe through which the rotary bit may have. been lowered.

My invention provides a bit that, among other things. overcomes the above stated slun'teomings of an ordinary bit. But the ma jor practical accomplishment of my invention is that my bit is capable of passing through a hole smaller than it itself drills. Passing through a pipe and drilling a hole large enough to take the pipe is one illustration of this. But the more common situation occurs where a bit must go down through a relatively small bore hole to reach the bottom where it is to begin to drill. In boring a well, for instance with a disk bit, the disk cutters Wear away as drilling progresses until a substantial reduction in the size of hole has taken place. For instance, a hole may be started'at fifteen inches diameter, but due to cutter wear be reduced to thirteen inches at say a thousand feet depth. The cutters are then so far worn they have to be renewed or a new bit put in. The operator has only the alternative of renewing the cutters to their original size or of using a smaller size bit. If he does the first he has to ream a great portion of the hole to ROTARY BIT.

2, 1926. Serial no. 85.446.

reach the bottom; if he does We second he then starts to drill a thirteen inch hole at a thousand foot level and upon reaching the two thousand foot level has only an eleven inch hole. and so his hole will gradually decrease in size all the way down.

- My bit, however, when the cutters are renewed after wear, will freely pass down through the diminished parts of the drilled hole, reaching bottom without any reaming, and then drill a full size hole beginning at that point. The hole is thus kept from diminishing in size from top to bottom. And when the bit is withdrawn it will as easily pass the diminished portions; and likewise will pass freely any places in hard formation Where an ordinary bit is likely to be pinched and its cutters injured.

It is a general object of the invention to provide an expansible bit that will do all these things; and, at the same time, a bit that is simple in structure. strong and rigid, and simple in operation. The invention is applicable to bits having various kinds of cutters and. although not limited thereto, lends itself particularly to rotary bits of the disk type. Thus the preferred embodiment of the invention is one utilizing rotary disks as cutters; and I will further describe a typical embodiment of the invention with cutters of another type. In order to make the invention clearly understood I describe preferred and illustrative forms of its embodiment in the following detailed specification. reference for that purpose being had to the accompanying drawings, in which: I

Fig. l is a vertical central section of a retary bit :urcording to my invention;

Fig. 2 is a vertical section taken as indicated by line 2 2 on Fig. -l; i

Fig. 3 is a vertical section taken as indicated byline 33 on Fig. 1;

Fig. -1- is a fragmentary elevation taken as indicated by line 4-4 of Fig. 1; Fig. 5 is a section online. of Fig. 1;

Fig. 6 is a vertical section like that of Fig. 1 showing a modified form Fig. 7 is a vertical section like that of Fig. 3 showing another modified form; and

Fig. 8 is a vertical section on line 88 of Fig. 7. In the drawings I show at 10 a shank of mandrel 10 that may be in any preferred form and configuration, having at its lower end two spaced legs or depending mandrel portions 11 between which cutting disks D are located. It will be understood that for the purposes of typical illustration herein the rotary bit is shown in that form having two spaced legs with the cutters located inside the legs. Other forms of rotary disk bits sometimes have a single and centrally located downwardly extending leg with the rotating disks located outside the single leg; but the application of my invention to such a form of bit will bewell understood by those skilled inthe art.

Each leg 11 carries a pin 12, the details of which will be hereinafter described. Upon each pin 12 there is rotat-ively mounted a circular eccentric 13, and upon this eccentric a disk D is rotatively mounted. Each eccentric 13 has a flange 14, concentric with the cccentric, and this flange 14 is locatedin a recess 15 in the inner surface of leg 11. Flange 14 is provided with a projecting stop lug 16 that limits the rotation of the eccentric be tween two shoulders 17 and 18. In the position in which lug 16 contacts with lower stop shoulder 17 the center of the eccentric is at the point denoted a on the line AA lVhen stop lug 16 is in contact with'the upper stop shoulder-18 the center of the eccentric is at the int denoted b on the line BB. It win noted that in rotation between these two positions the center of the eccentric is thrown upwardly and outwardly from position a to position b; and it will also be noted that at the position a the center of the eccentric is not quite directly below the center of pin 12 about which the eccentric rotates. In the position of the eccentric center at point 6 that center is substantially in the same horizontal plane as the center of pin 12, so that in that position the eccentric center at the point 6 is as far removed as possible, horizontally, from the vertical plane passing through the center of pin 12, and the disk D, carried on the eccentric, is thus as far removed outwardly as is ossible from the vertical center of the man rel or body of the bit.

In the particular form of bit illustrated in Figs. 1 to 5 it will be noted that the central axis of one of the pins 12 is to one side of center line C*C of the mandrel, while the other pin 12 is at the opposite side of that center line. Thus, even when the two eccentrics are in position with their centers very nearly below the centers of their respective pins, the two disks D are in this design not in co-axial alignment, one disk D projecting outwardly further to one side and the other projecting outwardly further to the opposite side of the mandrel. This is shown in Fig. 4 where the the two disks are shown in what I call their contracted positions. In Fig. 3 the disk D (the one that is shown in dotted lines in Fig. 2) is shown in its expanded position, the expanded position of the eccentric being therein shown in dotted lines. It will be seen that the eccentric of this particular disk D, in the aspect of Figs. 2 and 3, rotates in a counterclockwise direction to move from the contracted to the expanded position; and from an inspection of Fig. 4 it will be noted that, viewed in the same aspect, the eccentric of the other disk I) (the one nearer the observer looking at Fig. 4) rotates in a clockwise direction to move from its contracted to its expanded position.

Under gravitational influence the two disks with their eccentrics will ordinarily assume the contracted position, the eccentrics hanging down in the position shown in Figs. 2 and 4. In this position the disks are relatively contracted and the bit may be lowered through a pipe or hole of given internal diameter. IVhen the disks are set down upon the bottom of the drill hole the resultant upward pressure of the drill hole bottom upon the disks tends to move them upwardly and outwardly, and to move the eccentrics upwardly and outwardly, to the expanded position. If there is sufficient pressure of the formation against the disks, they will be moved upwardly and outwardly to their limits and consequently to their maximum expansion, and a hole of the maximum size will be cut. The diameter of their maximum cut may be designed to be large enough to pass the pipe down through which the bit has been passed. Thus the bit may be, in effect, a rotary underreamer, although, as I have pointed out before, the major utility is that it can cut a full sized hole after it has passed down through a hole of diminished size.

The amount of outward and upward expansive movements of the disks may be made to depend upon the upward pressure of the formation against the disks. This upward pressure of the formation depends upon the effect ve weight placed upon the bit; and that effective weight, if the bit is fed downward uni formly, depends upon the softness or hardness of the formation being drilled. Thus in a soft formation the disks may drop downwardly and inwardly somewhat so that the disk will actually out a smaller size hole while in a harder formation the disk will be: forced upwardly and outwardly so as actually to cut a larger sized hole. By this kind of action the final resultant hole may be made to be of substantially uniform diameter through alternating hard and soft formatrons.

Although the disks of my bit are thus made to be expansible and contractible, they are ne ertheless mounted in the bit mandrel in such a manner as to be rigid as regards all drilling strains imposed upon them. The mechanism which I use for expansion and contraction has no looscnesses; the disks, in any position of the eccentrics, are not capable of any lost motion. They are at all times solidly mounted.

My preferred structure for securing pins 12 in the bit legs is also shown in the drawings. Each pin 12 is threaded at its outer end at into a nut 31 lying in a recess 32 in the outer face of the leg. Nut 31 and recess 32 are so shaped that the nut cannot rotate in the recess; for instance, the nut has I a projecting lug 83 fitting into a corresponding extension of the recess. The nut tits the recess as snugly as is practicable and its inner or under face bears flatly against the bottom face of the recess. And pin 12 fits closely through the hole 34 in the leg; so that the pin is thus rigidly mounted in the leg. To lock the pin into the nut I provide a locking bolt 35 that extends through a central bore 'in pin 12 and screw threads at 36 into nut 31, the threads of locking bolt 35 being cut'i'n a direction opposite to those of pin 12. Looking bolt 35l1as a head 36 outside head 37 of pin 12; and when the pin and locking bolt are screwed home the head 36 maybe rotatively locked to head 37 by a set screw 38.

Although in the form shown in Figs. 1 to 5 I show the centers of the two pins 12 horizontally offset from each other, and thus show the two disks D horizontally offset from each other even when in contracted position, it is one of the features of my expansible construction that such horizontal offset of the two disks may be, if desired, obtained entirely by their expansive motions. Thus it is possible to set the axis of the two pins 12 on one and the same center line, and thus possible to use asingle central pin instead of two separate pins. Such a structure is shown in Fig. 6, where I show a single eccentric carrying pin 12 mounted between two legs 11, the two disks D being mounted on two eccentrics 13 the same as before described. Here, however, the construction allows of the two disks 1) being mounted in planes very close to each other, with only a bearing washer 40 separating them. Thus it will be seen that my expansive structure lends itself very readily to the placement of the two disks in planes very close to each other; and because it does this, s

it makes it possible to construct legs 11 very heavily within the diameter ofcut of the two disks.

In Figs. 7 and 8 I illustrate still another form of structure, in which the rotating disks are replaced by a non-rotative cutting blade 45. Each blade is mounted as before upon an eccentric 13 of the same kind as before explained, and the eccentric rotates between positions with its center at the points denoted a and b. In the lower position of the eccentric the blade is in the position indicated by dotted lines in Fig. 7, while in the upper or expanded position the blade is in the position indicated by the full lines in that figure. The blade has an upper diagonal edge 16 that bears against a ledge shoulder 47 on the inner surface of the leg 11 and this ledge shoulder and the diagonal blade edge are parallel to the line a?); so that the diagonal blade edge will bed against thediagonal ledge shoulder in both the contracted and expanded positions of the blade. Thus in both these positions the blade is rigidly held against any lost motion. being fixed in position by its bearing upon the eccentric and its bearing against ledge shoulder 17. The act ion of contraction and expansion of a bit of the type shown in Figs. 7 and 8 is the same as before described for the disk form.

It will be noted that recess 15 has its peripheral wall 15so shaped that, when the eccentric is in its outermost or expanded position, the eccentric flange 14 beds upwardly against the wall 15? of the recess; this being the position in which stop lugs 16 bear upwardly against stop shoulder 18. Consequently, in this position, as well as in its contracted position and where the eccentric flange also beds in against wall 15, the eccentric has a broad and very firm bearing surface against the body of the bit; and the great upward thrust of the cutters, due to the great weight bearing the cutters down onto the wall bottom, is thus taken off the pin '12 and is borne directly by the eccentric bearing and thus transmitted directly from the cutters through the eccentric to the body. The pins are thus protected against the great strain to which they are usually subjected, and are protected against bending or shearing.

Furthermore, the bedding of the eccentrics in their recesses, and particularly with their flat faces of contact with the flat back wall of the recesses, greatly strengthens the pins against the strains which they. are subjected to by reason of torsional action.

And another advantage that flows from such construction is that the rotary disk cutters have large and brbad bearing surfaces where they rotate upon the eccentrics. the wearing life of these hearings being thus very much increased over the usual wearing life of a rotating disk cutter mounted directly on a pin. t

I have referredhereinbefore to the fact that the weight imposed upon the cutters, with the cutters resting upon bottom, tends to expand the cutters by throwing the eccentrics outwardly. Another thing that tends to expand the cutters and keep them expanded while the bit is in operation, is the rotation of the cutters themselves. In operation the disks rotate in the direction indicated by the arrow in Fig. 3; antlthis is the direction in whichtheeccent rics rotate to expand the. bit. Consequently, the frictionalefl'ect of the cutters on the eccentrics is to rotate the eccentrics to their expanded positions: and thus, both the imposed weight and the disk rotation tend at all times to keep the disks in expanded positions.

The disk cutters, mounted upon each eccentric, are confined laterally between the lll) eccentric flange 14 and a washer 14, which fits over pin 12 and bears against the end of the eccentric and is rotatively locked to the eccentric by a lug l3 on the eccentric, which projects through a corresponding hole 14" in the washer. The disk is a little loose between flange 14 and washer 14, so that it rotates freely; and head 37 of pin 12 holds the washer against the end face of the eccentric and holds the eccentric back in flat bearing engagement with the flat rear wall of recess 15. but allowing a slight looseness, so that the eccentric is also freely rotatable on the pin.

I have mentioned before that the disks, in all their positions, although expansively movable, are solidly mounted and set; and it will be seen from the foregoing description that at no time are any adjustments necessary. The expansion and collapsing action are both entirely automatic. The disks may be worn out quite completely and still leave the hole approximately as large as the casing through which the bit is raised and lowered. In the case of an ordinary disk bit, the maximum size of a hole which the bit can drill is only as large as the inside of the casing through which thebit is lowered. And, as such a bit wears, the hole grows smaller. This results in the necessity of reaming out the hole from time to time, entailing a large amount of labor and waste of time, which my bit obviates. In case a bit is twisted off, with an ordinary bit where the hole is of reduced diameter, a fishing tool that will go down through the casing oftentimes cannot be put down through the hole of reduced size to reach and pick up the bit. \Vith my bit the hole is always large enough to pass any fishing tool that can go down through the casing.

Another advantage inherent in my bit is that more hole may be out due to the fact that larger disks may be used, thereby giving a greater length of cutting edge. The use of larger disks is due to the fact that the disks are expansible, as hereinbet'ore described.

I claim:

LAn expausible rotary bit, comprising in combination a mandrel, a bearing pin mounted on a substantially horizontal axis on the .mandrel and rigid with relation thereto, a

cutter carrying eccentric mounted on and rotatable on said pin, said eccentric and the mandrel having co-acting stop shoulders that limit the rotation of the eccentric between positions where the eccentric center is somewhat to one side of a position directly below the center of the pin and a position in which the eccentric center is substantially in a horizontal plane with the center of the pin, and a cutter carried on said eccentric, and

a downwardly facing shoulder on the mandrel against which the body portion of the eccentric bears when it is in the last-named position.

2. A11 expansible rotary bit, comprising in ly below the center combination a mandrel, a bearing pin mounted on a substantially horizontal axis on the mandrel, and rigid with relation thereto, a cutter carrying eccentric mounted on and rotatable on said pin, said eccentric and the mandrel having co-acting stop shoulders that limit the rotation of the eccentric between positions in which the eccentric center is somewhat to one side of a posit ion directly below the center of the pin and a position where the eccentric center is substantially in a horizontal plane with the center of the pin, a downwardly facing shoulder on the mandrel against which. the body portion of the eccentric bears when it is in the last-named position, and a rotary disk cutter rotatively carried on said eccentric with the center of the disk substantially coincident with the center of the eccentric.

3. An expansible rotary bit, comprising in combination a mandrel, a bearing pin mounted on the mandrel on a substantially horizon tal axis and rigid with relation to the mandrel, the pin projecting beyond one face of a part of the mandrel and that face having a recess provided with stop shoulders, a circular eccentric rotatably mounted on the pin, said eccentric having a flange located within said recess and the flange having a projecting stop lug coacting with said stop shoulders to limit the rotation of the eccentric between a position where the center of the eccentric isfsomewhat removed from a position directof the pin and a position substantially in the horizontal plane of the pin center, and a rotating disk mounted on and carried by the eccentric, the disk being freely rotatable, upon the eccentric and the center of the disk being substantiallycoincident with the center of the eccentric.

4. In a disk bit,'a mounting for a hearing pin in a mandrel, comprising a mandrel portion having a non-circular recess, a correspondingly shaped nut fitting the recess and into which the end of the pin is screw-threaded with threads cut in one direction, the pin having a longitudinal bore through it from end to end, a locking bolt extending through the pin and screw threaded into the nut with threads cut in the opposite direction, a head on the locking'bolt, and means for locking the bolt head against rotation with relation to the end of the pin.

5. An expansible rotary bit, comprising in combination a mandrel, an eccentric mounted to rotate eccentrically on a substantially horizontal axis on the mandrel, stops coacting between the mandrel and the eccentric to limit rotation of the eccentric to approximately one-quarter of a revolution, bearing surfaces in the mandrel against which the eccentric beds when in limiting positions, and a cutter mounted upon and carried b said eccentric.

6. An expansible rotary bit, comprising in combination a mandrel, an eccentric mounted to rotate on a substantially horizontal axis on the mandrel, stops coacting between the mandrel and the eccentric to limit rotation of the eccentric to approximately one-quarter of a revolution, bearing surfaces in the mandrel against which the eccentric beds when in limiting positions, the exterior surface of.

the eccentric being cylindrical, and a rotating disk cutter rotatably mounted upon and carried by the eccentric.

7. An expansible rotary bit, comprising in combination a mandrel having therein an eccentric receiving recess, an eccentric rotatably mounted upon the mandrel in said recess and rotating upon a substantially horizontal axis, stops coacting between the mandrel and eccentric limiting the movement of the eccentric to approximately one-quarter of a revolution, the wall of the recess being so shaped that the eccentric in one limiting position bears upwardly against said recess wall, and a cutter mounted upon and carried by said eccentric.

8. An expansible rotary bit, comprising in combination a mandrel, a bearing pinmounted on the mandrel on a substantially horizontal axis and rigid with relation to the mandrel, the pin projecting beyond one face of a part of the mandrel and that face having a recess provided with stop shoulders, a circular eccentric rotatably mounted on the pin, said eccentric having a flange located within said recess and the flange having a projecting stop lug coacting with said stop shoulders to limit the rotation of the eccentric between a position where the center of the eccentric is somewhat rcmoved from a position directly below i the center of the pin and a position substantially in the horizontal plane of the pin center, the upper wall of said recess being so formed that when the eccentric is in its second mentioned position the eccentric flange beds firmly upwardly against said recess wall, and a rotating disk mounted on and carried by the eccentric, the disk being freely rotatable upon the eccentric and the center of the disk being substantially coincident with the center of the eccentric.

In witness that I claim the foregoing I have hereunto subscribed my name this 19th day of January, 1926.

ARTHUR ALLISON. 

